1. Field of the Invention
The present invention relates to an image processing technique for generating composite image data based on variable data and fixed data.
2. Description of the Related Art
In recent years, variable print processing that applies blend print processes of a plurality of variable data to fixed background image data is used. Particularly, instances that implement variable print processing having an appealing visual effect to customers by applying a transparent effect are increasing.
There are some page description languages (PDL) which can provide a transparent effect to objects. For example, with the PDF format of Adobe Systems Incorporated (see PDF Reference, 5th Edition, Version 1.6, Adobe Systems Incorporated, ISBN: 0-321-30474-8), background and transparent objects can undergo transparent effect processing and can be displayed on a display or can be printed. Also, various page description languages for efficiently implementing printing using variable data have been developed. For example, PPML (Personalized Print Markup Language) defined by PODi (Print On Demand Initiative) is available (see PPML Functional Specification, Version 2.1 (http://www.podi.org/)). With these page description languages, a non-variable region that has undergone rendering processing is cached on a storage device. Then, a variable region that has undergone the rendering processing is blended to the readout cached object, thus controlling to attain high-speed processing while avoiding the non-variable region from repetitively undergoing the rendering processing.
However, in general, enormous floating-point calculations are required to execute the transparent processing. For this reason, in variable print processing including transparent processing, the processing time increases greatly. Particularly, in commercial print processes required to attain high-speed print processes despite a huge number of records, a desired print speed cannot often be attained. In particular, in variable print processing in which a background object is a complicated image like a photo image, and foreground transparent objects are defined as variable data, the transparent processing needs to be applied for each pixel of the background image, and the print speed drop is serious.